Experimental evidence is emerging that the gasotransmitter hydrogen sulfide serves an important role in the cardiovascular system especially during tissue ischemia. However, specific cellular sources, targets, and mechanisms of hydrogen sulfide within the vasculature remain largely unknown. Work from our lab and others demonstrate that hydrogen sulfide is protective against chronic tissue ischemia, which involves increased vascular remodeling responses such as angiogenesis. Importantly, very little mechanistic information exists regarding how hydrogen sulfide modulates ischemic vascular remodeling in vivo or in vitro. Data in this application reveals a novel finding that hydrogen sulfide emanating from cystathionine !-lyase (CSE) selectively augments ischemic tissue nitrite reduction to NO that mediates increased angiogenic activity involving HIF-1 activity and VEGF expression. Experiments in this proposal will determine molecular mechanisms for these novel results through the hypothesis that endothelial cell CSE dependent hydrogen sulfide generation augments ischemic nitrite reduction to NO that increases ischemic vascular remodeling. The hypothesis will be examined through the pursuit of three specific aims including: 1) determine how endothelial cell CSE expression regulates ischemic vascular remodeling responses, 2) determine the mechanisms by which hydrogen sulfide increases NO generation in ischemic tissue and how this regulates HIF-1 activity and VEGF expression, and 3) determine the effect of endothelial cell CSE dependent hydrogen sulfide on diabetic ischemic vascular remodeling responses. Successful completion of this project will significantly advance the fields understanding of hydrogen sulfide biology in the vascular system, provide clear mechanistic information on hydrogen sulfide-NO pathway interactions, and identify novel approaches for ischemic vascular disease therapy. PUBLIC HEALTH RELEVANCE: Peripheral ischemic vascular disease (e.g. Peripheral Arterial Disease (PAD) is a chronic disorder associated with reduced blood flow to the extremities, which results in serious complications such as critical limb ischemia, limb amputation and in some cases may lead to death. Individuals with PAD suffer from endothelial cell dysfunction and lack of bioavailable nitric oxide (NO). Moreover, patients with diabetes are also at a greater risk of developing PAD. Work from our laboratory has discovered that hydrogen sulfide selectively increases endothelial cell NO bioavailability through a novel mechanism of nitrite reduction back to NO. Studies in this proposal will identify critical endothelial cell enzymes regulating hydrogen sulfide formation and subsequent NO formation. These results will identify novel molecular targets for potential therapeutic interventions directed at peripheral ischemic vascular disease.